1. Field of the Invention
The present invention relates to a communication apparatus, a control method therefor, and a storage medium.
2. Description of the Related Art
Some communication apparatuses are configured to be capable of making phone calls by not only using a circuit-switched telephone network (hereafter referred to as the PSTN) with a FAX modem but also switching a line to a phone or a handset which supports the PSTN and using the PSTN with the phone or the handset when the communication apparatuses are capable of carrying out FAX communications supporting the PSTN (see, for example, Japanese Laid-Open Patent Publication (Kokai) No. H03-22747).
Such communication apparatuses are equipped with not only a modular jack for connecting to a PSTN but also a modular jack with the same shape for connecting a phone or a handset thereto.
Also, the communication apparatuses described above are generally equipped with a plurality of standby modes in which they are waiting to receive a fax or a phone call. Examples of such modes include an automatic receiving mode in which a fax is automatically received, a fax/telephone switching mode in which whether an incoming call is a fax or a phone call is determined, when the incoming call is a fax, a fax is received, and when the incoming call is a phone call, a phone is called, and a ring setting mode in which a phone is caused to ring, prompting a user to determine whether an incoming call is a fax or a phone call.
Among these modes, in the automatic receiving mode or the fax/telephone switching mode, an interface for a phone or a handset is shut off from power fed from the PSTN or a TA (terminal adaptor). In order to, in such a case, detect an off-hook state of a phone or a handset and output a phone ringing signal, there is a technique to supply power from a communication apparatus to an interface for the phone or the handset (see, for example, Japanese Laid-Open Patent Publication (Kokai) No. H06-150396).
Moreover, in recent years, IP-FAX which is the technique to replace a conventional PSTN with a network based on the IP (internet protocol) technique and offer services on a LAN or a next generation network (NGN) has come into widespread use. For IP-FAX machines which are communication apparatuses using this technique, an Ethernet (registered trademark) cable called RJ45 is used in connecting to a LAN or an NGN.
The IP-FAX machines as well are equipped with a modular jack and a circuit which supplies line voltage to a phone or a handset and outputs a phone ringing signal so that the phone or the handset which has been used on a PSTN can be used. This enables the IP FAX machines to convert analog voice data which is handled by a phone or a handset, and digital voice data which is handled by a LAN or an NGN and enables phone calls.
However, communication apparatuses for use on a PSTN are equipped with two types of modular jacks with the same shape (for a PSTN/TA and for a phone/handset), and hence there may be cases where a modular cable for connecting with a PSTN or a TA is improperly connected to the modular jack for a phone/handset, not to the modular jack for a PSTN/TA.
In IP-FAX machines, a connector called RJ45 is used for an IP-FAX interface, and the IP-FAX machines are equipped with a conventional modular jack as well as a connector for connecting a phone or a handset. Thus, there may be cases where a modular cable which connects to a PSTN or a TA may be improperly connected to this conventional modular jack.
When a modular cable which connects to a PSTN or a TA may be improperly connected to an interface for a phone or a handset, an unexpected DC 48-V voltage or voltage not less than AC 100 V which is a voltage of a phone ringing signal is applied.
Moreover, when power is being fed from a communication apparatus to an interface for a phone or a handset, power fed from a PSTN or a TA and power fed from the communication apparatus to the phone or the handset conflict with each other. If this situation arises, a power feeding circuit of the PSTN or the TA and a power feeding circuit of the phone or the handset for the communication apparatus may fail.
As described above, according to the prior arts, events such as troubles and failures may occur due to improper connection.